Eye (biophysics)/Principle of vision

The eye is a combined optical system with a variable focal length. The resulting image is reduced, inverted and real.

• when the beam enters the eye, the light passes through the cornea and ocular fluid
• variable opening in the iris controls the intensity of incident light
• after passing through the lens (the largest refractive index of all parts of the eye) the light spreads with the vitreous (smallest refractive index)
• the image formed on the retina, in which there are two types of cells:

1. rods (perceive light intensity)
2. cones (perceive colors)

Here are the endings of the of the optic nerve, that carry sensations to the brain.

• two main points are used to orient the eye doctor on the retina:

1. yellow spot (macula lutea) – the place of greatest eye sensitivity
2. blind spot (discus nervi optici; papilla nervi optici) – place where the optic nerve enters the eye, i.e. a place where there are no sticks or suppositories

• the emergence of a sharp image is made possible by accommodating ability of the lens, which is held by the ciliary muscle, which changes the curvature of the optical surfaces as needed (at a long distance, less curvature and vice versa):

• when looking at a far point (infinity) the accommodation of the eye is minimal
• when looking at the near point (up to 15 cm), the accommodation of the eye is maximum

• Conventional visual distance = 25 cm.

Links

Related articles

• Biochemistry of the vision process
• Trichromatic Vision
• Eye (biophysics)
• Eye (biophysics)/Eye defects
• Ocular muscles
• Eye (histology)
• Retinal detachment

Source

• Holešov. Ladislava Jaroše Gymnasium [online]. [cit. 2009-05-23]. <http://www.gymhol.cz/projekt/fyzika/07_soustavy/07_soustavy.htm>.

External links

• Kymplová Jaroslava: Biophysics visions. Multimedia support for the teaching of clinical and medical fields :: Portal of the 1st Faculty of Medicine of Charles University in Prague [online] 2/19/2008, last update 2/19/2008 [cit. 2011-12-22] Available from WWW: <https://portal.lf1.cuni.cz/clanek-809-biofyzika-videni>. ISSN 1803-6619